In the repair and replacement of large tire and rim assemblies, such as the kind used in off-road heavy equipment, it is usually necessary to use considerable force to dislodge the tire beads from the rim to remove the tire. In the early stages of development in this art, hand tools such as a prybar and mallet were used to forcibly loosen the tire bead. However, not infrequently, use of such tools was time consuming and resulted in damage to the tire wall or rim assembly.
As the size of tire and wheel assemblies have increased, a significant number of specialized pneumatic, hydraulic or manual bead loosening tools have been introduced. Representative of these specialized tools are Northrup et. al. U.S. Pat. No. 2,520,330; Woodward U.S. Pat. No. 2,900,016; Pile et. al. U.S. Pat. No. 3,344,833; and Bunts U.S. Pat. No. 3,880,220. These patents disclose tire bead loosening tools which employ a means to fixture the tool to the rim and a pressure foot or plunging member to apply force against the tire wall or tire bead retaining flange to loosen the tire bead. An adapter for mounting a bead loosening tool to a normally incompatible rim construction is disclosed in Robinson et al U.S. Pat. No. 4,462,450.
The aforementioned tools conventionally employ various means to fixture the tool to the wheel rim. In the Northrup '330 patent, the fixturing means is comprised of a simple clamping mechanism. To mount the tool to the one-piece tire rim, a spaced-apart pair of hooks integral with the tool is placed between the inner rim and tire bead. A long-handled, resiliently-padded, pivotally connected member is then rotated downwardly with the resilient pad abutting against the axially outer surface of the rim tightly gripping the rim between the pad and the hooks. The clamp also functions to position the tool so that the applied plunger force is directed generally inwardly against the tirewall to loosen the bead from the rim. However, without the application of a considerable amount of manual force to the clamp handle during use, the clamp may loosen and disengage from the rim. Additionally, undesirable and potentially dangerous bodily pivotal tool movement during operation is possible because of an unrestrained moment created around a pivot point formed where both hooks engage the rim. Finally, lack of significant axial and radial adjustment limits the commercial application of this tool to primarily unitary rims of simple construction.
Woodward '016 discloses a tool with fixturing means comprising two pairs of spaced apart, opposing chisel-pointed rim clamp jaws for mounting the tool to the tire bead seat retaining flange of a wheel rim and a pivotable and adjustable T-handled screw for stopping against the lock ring of the rim for preventing tool rotation during operation A pair of screws in communication with both jaws are provided to engage and disengage the jaws from the tire bead seat retaining flange. A serious drawback of this design lies in the moment created around the T-screw point of contact with the lock ring, resulting in considerable force attempting to pull the clamp jaws off the rim. Any decrease in retaining flange surface friction or jaw clamping force can result in sudden, dangerous, potentially catastrophic clamp jaw disengagement. The mounting mechanism of this tool also lacks sufficient axial and radial adjustment for fixturing the tool to a wide range of off-road vehicle wheel rims.
In Pile '833, the fixturing means comprises a spaced apart pair of hooks engaging a corresponding pair of U-shaped brackets weldably attached to both tire bead seat retaining flanges of one type of wheel rim. To loosen the tire bead from the rim, the hooks are inserted into the U-shaped brackets and the spade-tipped plunger is manually positioned with its end directed into the crease between the tire sidewall and the bead seat retaining flange directly engaging the sidewall. Affirmative interlocking of the hooks with the brackets is provided by outwardly extending the spade-tipped plunger until it forcibly contacts the tire side wall. However, during use, the tool can pivot bodily, causing the hooks to disengage and injure the operator. Such tool movement may also change the plunger force direction thereby frustrating efforts to loosen the tire or even resulting in damage to the tire wall or wheel rim assembly. Finally, this tool is only adaptable to rims with U-shaped brackets mounted around the outer radial periphery thereon or, at best, with a very limited range of rim assemblies having specifically conforming mounting flanges
A bead loosening tool for use with a specific off-road-vehicle-wheel rim configuration is disclosed in Bunts '220. To mount the tool, a pair of spaced-apart hooks engage an annular offset of the rim and one end of a bolt carried by the tool abuts against the axially outer face of the rim base or a removable bead seat band to prevent bodily tool rotation during use. Unfortunately this tool is not sufficiently axially nor radially adjustable with respect to the rim assembly for use on a great number of rim configurations.
Also relevant because of its ability to adapt an existing bead loosening tool for mounting the tool on a normally incompatible rim design is the tire bead loosening tool mounting adapter found in U.S. Pat. No. 4,462,450, Robinson et al. Robinson, et al '450 discloses an adapter plate to enable an existing tire bead loosening tool, without modification, to be mounted on a type of off-road vehicle wheel rim configuration having at least one tapered axially outer rim base surface.
Thus, although the aforementioned tire bead loosening tools and mounting adapter having been successfully built and used on various wheel rim configurations, certain problems nevertheless remain, such as poorly designed clamping or fixturing means generally providing poor reaction support to the tool while fixtured to the rim, rather loose engagement of the tool with the rim, and unacceptable radial and axial fixture adjustment limiting adaptability to generally only one type of rim configuration. Poor or inadequate reaction support can cause sudden, undesirable, or unsafe bodily tool movement during use, possibly damaging the wheel rim, puncturing the tire wall or seriously injuring the user. Loose or unstable engagement with the wheel rim can force the tool to suddenly disengage, again producing injurious conditions for the user. Finally, the limited adaptability of these tools to new and different rim designs results in expensive and undesirable tool obsolescence as new and improved rim designs are introduced into the market place.